1. Field of the Invention
The present invention relates to a novel support for a magnetic recording disk and to the process for the production thereof. It is more particularly used in the production of magnetic disk computer memories.
2. Discussion of Background
The supports for recording disks are metal wafers having a central hole and cut from a metal sheet having a thickness of a few millimeters, usually made from an aluminium-based alloy.
Before being covered by the magnetic coating to contain the information, said supports undergo a mechanical and chemical preparation giving them a surface state of an adequate quality to ensure that the magnetic coating covering them has a minimum of defects.
The mechanical preparation generally consists of smoothing the two faces by means of a turning operation. This leads to micro-grooves, which have micro-roughnesses, which can then be eliminated by fine polishing or anodic oxidation.
Despite the high cost of these operations, the surface state obtained is not of an adequate quality of permit the deposition of magnetic coatings containing the information with a high recording density. In order to increase this density, it has been proposed to cover the metal disks with a polymer layer. This layer is firstly spread out in the form of a prepolymer by means of a centrifuging operation and is then heated for polymerization purposes. Such a procedure is e.g. described in European Pat. No. 0 055 819, published on July 14th 1982 and entitled "A method for providing a layer of polymeric material on a substrate".
Although such a procedure improves the quality of the supports obtained, it is not free from defects. Thus, the magnetic disks produced therewith only have a limited life. The Applicant considers that the partial and progressive loss of the information contained in such disks is due to the fact that the polymer layer is a relatively soft material and that the magnetic coating covering the polymer can deform under the pressure exerted by the read head when the latter rubs against the dust particles which are inevitably deposited on the face of the disk. These repeated deformations end up by destroying complete sectors of the magnetic coating.